1. Field of the Invention
The present Invention relates to a fire extinguisher system. More specifically, the present invention relates to a fixed fire extinguishing system delivering an inert gas composition suitable for use in occupied spaces by means of a particular combination of stored gas containers and solid propellant inert gas generators to provide the most compact system possible.
2. Related Art
Halogenated fluorocarbon gases such as bromotrifluoromethane (CF.sub.3 Br) have been used to provide fire extinguishing capability for the majority of this century. These gases, which chemically inhibit fires, provide high efficiency and compact systems that can be placed in small storage areas. In addition, the very low toxicity of such substances has allowed their use to protect compartments normally occupied by humans, such as computer rooms, libraries and vehicles. These applications comprise a large portion of the fire protection market. Unfortunately, recent discoveries of stratospheric ozone depletion attributed to such substances have resulted in international actions to eliminate production and some uses now and in the future.
As a result, new alternative technologies and techniques have been sought to provide fire protection for such applications and anywhere halogenated fluorocarbons have been traditionally used, while preventing further ozone depletion. In the last eight years, several products have emerged to provide niche answers to many of the applications of halogenated fluorocarbons in fire protection. However, such products have not shown the same degree of low toxicity, physical properties and fire extinguishing efficiency and performance in combination as the halogenated fluorocarbons. This lack of equivalent fire extinguishing performance is predominantly due to the lack of chemically active fire extinguishing capability, since the halogen component (the chemically active member) of earlier products has also been attributed as the ozone depleting component. As a result, new environmentally safe technologies generally cannot utilize such halogens, to avoid their release into the atmosphere. Such new products typically require much more space and weight allowances than the halogenated fluorocarbons they replace. Among these products, only a select few have been approved for use in occupied spaces by regulatory authorities such as the Environmental Protection Agency, since these products tend to have higher toxicities than the halogenated fluorocarbons. These few products with acceptable toxicities for occupied space use suffer from measurable storage space increases over their predecessors, which make additional demands on new installations and can make retrofit systems very difficult. In addition, most of these products have calculated or measured long atmospheric lives, which can contribute to global warming. This feature currently limits their use in some applications, and they may face further restriction in the future.
A select class of products that do not suffer such toxicity or environmental effects are the compositions of inert gases for fire protection. Traditional pure inert gases, such as nitrogen or carbon dioxide, used by themselves cannot inert and extinguish fires at concentrations that allow humans to function, since they must decrease the oxygen concentration below a level that supports human activity. Recent discoveries, however, have shown that blended compositions of such gases can be formulated to support human function while extinguishing fires. One particular composition, labeled IG-541 by the U.S. Environmental Protection Agency Significant New Alternatives Program (SNAP), has achieved such capability by blending a mixture of nitrogen, argon and carbon dioxide in a ratio of 52%:40%:8% respectively to extinguish fires, yet support human activity by increasing the human respiration rate with the addition of carbon dioxide, so that sufficient oxygen can be inhaled in necessary quantities.
This concept has been demonstrated and withstood extensive medical review. This composition is now being widely distributed around the world for enclosed space total flood fire extinguishing systems with the potential for human occupancy. One significant drawback, however, is that the large storage spaces required for the compressed gas tanks may require almost ten times the space of previous halogenated fluorocarbon systems. This severely limits its use for many applications and for retrofit into existing installations. Other inert gas compositions exist which suffer from the same limitations.
In summary, a technology is desired that can retain the beneficial features of the inert gas fire extinguishing compositions in terms of human safety, effectiveness and environmental acceptability, while reducing the detrimental feature of large increases in required storage area, to facilitate wider implementation of such technologies. No device has been demonstrated to date that incorporates all of these features.